An influenza epidemic is sweeping the nation, with more cases and hospitalizations this year, and a less effective vaccine for the strain.

The Centers for Disease Control and Prevention say 43 states, including Massachusetts, have high or widespread outbreaks. Flu-like symptoms accounted for nearly 6 percent of all doctor visits nationally in the last week of 2014, and higher hospitalization rates than this time last year, with 12.6 people per 100,000 being treated for the flu.

Dr. Anita Barry, director of infectious disease for the Boston Public Health Commission, said the city has seen an upward surge in both the number of influenza reports.

"The last few weeks in the city we've seen it trending on an upward path. We expect to be seeing a lot more of the flu in coming weeks," said Barry.

This year’s predominant strain, H3N2, was prevalent during the 2012-2013 flu season, when 13.3 per 100,000 people were hospitalized for the flu, according to the CDC. Health professionals say the vaccine is only about 60 percent effective, but decreases the severity of flu-symptoms, which include fever, cough and runny nose, aches and fatigue.

"The message here is to get vaccinated," said Barry. "And do everything you can to take preventative measures."